Species composition, distribution patterns and population structure of penaeid shrimps in Malindi-Ungwana Bay, Kenya, based on experimental bottom trawl surveys

Population structure and distribution of the starry ray, Raja asterias, were described based on data collected during yearly rapido trawl surveys (SoleMon), between 2005 and 2014 in the Northern and Central Adriatic Sea. A total of 306 individuals were caught, sex ratio was 1.04:1 in favor of males and length-weight relationships were obtained for the whole sample. Following the MEDITS scale, maturity was estimated, observing a higher number of immature individuals. Relative abundance significantly increased during the recent period with the highest values recorded at 5-30 m depths. Such increase could be related to the response of R. asterias to climatic change or to the decrease in fishing pressure in the area. Clear spatial segregation of individuals depending on their life stage was observed, with immature individuals inhabiting the coastal areas and adults more abundant at depths greater than 40 m. The comparison of the result of the present study with MEDITS survey outcomes in terms of distribution patterns, persistence areas of adults and juveniles and abundances indices, evidences that SoleMon survey seems to be more suitable in defining such features of the stock, likely due to the greater catchability of the rapido trawl in respect to the MEDITS trawl net. However, further investigations are needed to identify factors affecting the increasing abundance of this species, and develop an action plan for spatial management of fishing activities.

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Bathymetric distribution of macroinvertebrates in the Northeastern Levantine Sea and the Northeastern Aegean Sea based on bottom-trawl surveys

Oceanological and Hydrobiological Studies ◽

10.1515/ohs-2017-0040 ◽

2017 ◽

Vol 46 (4) ◽

Cited By ~ 1

Author(s):

Onur Gönülal ◽

Cem Dalyan

Keyword(s):

Aegean Sea ◽

Distribution Patterns ◽

Bottom Trawl ◽

Depth Range ◽

Bathymetric Distribution ◽

Levantine Sea ◽

Macroinvertebrate Species ◽

Trawl Surveys

AbstractThe objective of this study was to compare the distribution patterns of macroinvertebrate species between the Northeastern Levantine Sea and the Northeastern Aegean Sea. A total of 157 hauls were carried out by commercial trawlers at depths ranging from 30 to 410 m in both areas. The result of SIMPER analysis shows clear differences between the two surveyed areas except for the 300-410 m depth range. Ninety five species were found in the Northeastern Aegean Sea and 100 species in the Northeastern Levantine Sea. Of these species,

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Species composition, distribution patterns and ecological functions of biological soil crusts in the Gurbantunggut Desert

Journal of Arid Land ◽

10.3724/sp.j.1227.2010.00180 ◽

2010 ◽

Vol 2 (3) ◽

pp. 180-189 ◽

Cited By ~ 34

Author(s):

ZHANG YuanMing ◽

WU Nan ◽

ZHANG BingChang ◽

ZHANG Jing

Keyword(s):

Species Composition ◽

Distribution Patterns ◽

Biological Soil Crusts ◽

Gurbantunggut Desert ◽

Composition Distribution ◽

Ecological Functions ◽

Soil Crusts ◽

Gurbantünggüt Desert

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Determining species composition in mixed-species marks: an example from the New Zealand hoki (Macruronus novaezelandiae) fishery

ICES Journal of Marine Science ◽

10.1016/s1054-3139(03)00034-1 ◽

2003 ◽

Vol 60 (3) ◽

pp. 609-616 ◽

Cited By ~ 10

Author(s):

Richard L O'Driscoll

Keyword(s):

New Zealand ◽

Species Composition ◽

Bottom Trawl ◽

Mixed Species ◽

Model Based ◽

Good Potential ◽

Acoustic Contribution ◽

Catch Composition ◽

Mixed Layers ◽

Trawl Surveys

Abstract A model-based method has been developed for partitioning acoustic backscatter from mixed-species marks. This method uses catch-composition data to partition the echo integral, but allows for differences in trawl catchability and acoustic vulnerability between species. It was applied to estimate the biomass of New Zealand hoki (Macruronus novaezelandiae) from trawl and acoustic surveys on the Chatham Rise and Campbell Plateau in 2001. Mixed-species layers containing up to 20 different species were present in both survey areas. A total of 224 bottom-trawl surveys (123 on Chatham Rise and 101 on Campbell Plateau) were carried out to determine the species composition and relative densities. Simultaneous acoustic recordings made during each of these trawls were used to estimate vulnerability ratios for the two methods, i.e. acoustic as opposed to trawl surveys, (acoustic:trawl) by non-negative, least-squares minimization. The best-fit model for each survey attributed 14–22% of the backscatter in mixed layers within 10 m of the bottom to hoki. This produced hoki biomass estimates 1.3–1.8 times higher than the standard approach, which divides the echo integral in proportion to the catch assuming equal trawl catchability. The precision of the estimated acoustic:trawl vulnerability ratios depended on the contrast in trawl catch composition, and the ratios for the same species differed between areas. A major problem on the Chatham Rise was the acoustic contribution of small mesopelagic species, which are not caught by the bottom trawl. Despite these difficulties, the model-based approach has good potential for determining the biomass of the target species in a mixed-species mark when the different species cannot be discriminated acoustically.

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